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F. LJUNGSTRO'M, ELASTIC FLUlD TURBINE.

APPLICATION FILED 050.5. I9l8.

Patented Oct. 7, 1919.

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UNITED STATES PATENT FREDRIK LJ'UNGS'I'RfiM, OF STOCKHOLM, SWEDEN, ASSIGNOR TO AKTIEBOLAGET IJUNGSTROMS ANGTURBIN, A CORPORATION OF SWEDEN.

ELASTIC-FLUID TURBINE.

Specification of Letters Patent.

Patented Oct. '7, 1919.

Application filed December 5, 1918. Serial No. 265,407.

v To all whom it may concern:

Be it known that I, FREDRIK LJUNG- p srniiM, a subject of the King of Sweden, re- E siding at Stockholm, Sweden, have invented 5 certain new and useful Improvements in Elastic-Fluid Turbines, of which the following is a specification.

The present invention relates to elasticfiluidi turbines such as steam and gas turbines,

and particularly to the rotors or rotor members of such turbines which carry the blade or vane rings. One particular application of my invention is in connection with the rotors or rotor members of radial flow or combined radial and axial flow turbines and in the following specification it is specifically described in this connection. It will be understood, however, that the invention is not necessarily limited to turbines of this type.

0 Formachines of large outputthe rotors or rotor members of radial flow or combined radial and. axial flow turbines carrying the blade rings of necessity have considerablemass in orderto give the necessary strength 5 to withstand the heavy stresses set up therein and in some cases great difiiculty is experienced in properly heat treating them to obtain the necessary strength. In fact, in some cases the mass is so great that it has 0 been altogether impossible to evenly harden such rotors and as a consequence the material in them has not been homogeneous, the surface portions only being hard and the inner portion relatively soft.

5 The object of the present invention is to provide an improved rotor or rotor structure wherein'athe above referred to difliculty is overcome and for a consideration of what I believe to be novel and my invention, at-

0 tention is directed to the accompanying description and the claims appended thereto.

In carrying out my invention 1 construct the turbine rotor or rotor member of an intermediate or central plate and I reinforce 5 such central plate by means of two side disks,

one' arranged on each side of the centralplate, the two disks being connected with said central plate in any suitable manner so as to form a rigid construction; The central plate may and commonly does carry at its periphery a ring of radially extending blades. The central plate and the side. disks maybe connected together by means of a number of annular shoulders and grooves 5 or the like provided in such parts at different radial distances from the center and fitting one into another, the side surfaces of such shoulders and grooves being coiiperatlvely beveled. Preferably such shoulders and grooves are generally of dove-tail shape and are brought into interlocking engagement by means of shrinking the side disks on to the intermediate plate. In such an arrangement the side disks and the intermediate plate will act jointly to resist the stresses caused by rotation. In the accompanying drawing Figure 1 1s a radial sectional view of a turbine rotor embodying my invention, and Fig. 2 is an enlarged detail view of a portion thereof. Referring to the drawing the rotor is shown as comprising a central annular plate 5, reinforced on its two sides by disks 6 and 7 The disks 6 and 7 are rigidly fastened to the plate 5 by interlocking dove-tail shaped to the plate 5 by interlocking dove-tail shaped projections and grooves as indicated at 8. These interlocking parts, as will be clear, may be brought into engagement by shrlnking the side disks 6 and 7 on to the plate 5, and when thus shrunk into position the whole forms a rigid construction so that the tenslons set up in the plate 5 due to centrifugal forces will be in part transmitted to the side disks 6 and 7 and resisted by them,

The greatest strains due to centrifugal forces occur adjacent to the hub or bore of the wheel; The side plates 6 and 7 are accordingly made comparatively thick adjacent to their bores and gradually taper toward the peripheries. By this arrangement the wheel is at all points amply strong to withstand the stresses, while at the same time the least amount of material is used. Referring to Fig. 2, which is enlarged for illustration, it is to be noted that each annular projection or shoulder 8 on each side of the central plate 5 is undercut on its periphery as indicated at 9, While the innersurface thereof indicated at 10 is cylindrical. Also that the outer annular wall 11 of the groove in the side member 6 is beveled at the same angle as the surface 9 so that the parts will securely interlock. On the other hand the Wall 12 of the groove is cylindrical and is separated from the wall 10 by a space which is slightly greater than the amount that the pro ection or shoulder 8 is undercut at its periphery. This arrangement is necexpanded condition. \Vhen the disk cools it shrinks and the surfaces 9 and 11 are brought into firm engagement. As a result of this arrangement any load on the central plate due to centrifugal force is partially transmitted to the side members and any tendency for the disks to move axially is prevented. To prevent angular movement of the blade carrying disk 6 on the center plate, they may be united by suitable means as by calking, either at the periphery of the disk or at the bore.

In the present instance the plate 5 is shown as carrying a ring of radially extending buckets 13 and the side disk (3 is illustratcd as having attached thereto a plurality of rings of axially extending vanes or buckcts ll. 15 indicates the expansion ring which connects that portion of the rotating structure above described to the shaft.

By the above described arrangement the respective parts 5, 6 and 7 of the disk can be made separately and suitably heat treated so as to give them the desired strength and characteristics for a turbine rotor. At the same time, owing to the smaller dimensions, each of the respective members, 5, 6, and 7 can be much more advantageously forged or otherwise made. The completed rotor, however, will have the necessary size and strength to withstand the stresses to which it may be subjected.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative, and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. In an elastic fluid turbine, a blade carrying member comprising a central plate and a reinforcing side disk on each side of said plate, said reinforcing side disks each being comparatively thick at its center and tapering toward its periphery and connected to said central plate by a plurality of concentric interlocking dovetail projections and grooves.

2. In an elastic fluid turbine, a blade carrying member comprising a plate having a central bore, and a reinforcing disk also having a bore and connected to said plat-e by a plurality of interlocking dovetail projections and grooves, said reinforcing disk being con'iparatively thick at its bore and tapering toward its eriphery.

3. In an elastic-fluid turbine, a blade carrying member comprising a plate and a reinforcing side disk on each side of the plate, said side disks being connected to said plate by interlocking dove-tail projections and grooves, said projections and grooves being brought into engagement with each other by shrinking the side disks on to the plate.

4. In an elastic-fluid turbine, a rotor comprising a central member having annular projections on opposite sides which are undercut on their peripheral surfaces, and disks on opposite sides of the plate which have annular grooves, the outer wall of each groove making a shrink fit with a correspondin" undercutperipheral surface on a projection.

5. In a rotor for an elastic-fluid turbine, the combination of a central member-having annular projections on o-ppostie sides which are undercut on their peripheral surfaces, radially extending blades carried by said member, reinforcing disks on opposite sides of the plate which have annular grooves, the outer wall of each groove making a shrink fit-with a corresponding undercut peripheral surface on a projection, said undercut project-ions transmit-ting stresses from the plate to the disks and also anchoring the latter against axial 'movement, and a ring of blades which is carried by one of said disks.

In witness whereof, I have hereunto set my hand this 19th day of September 1918.

FREDRIK LJUNGSTROM.

Witnesses:

OsoAR GRAHN, F. E. HALLIN. 

